


Inverted Fate: Determined Hearts

by Shadowhisker



Category: Inverted Fate, Undertale (Video Game)
Genre: Alternate Ending, Alternate Universe, Gen, Inverted Fate - Freeform, Major Character Death is Implied, Mecha, Narrator Chara (Undertale), Probably ooc, Time Shenanigans, and quickly undone by, blatant excuse to have a giant robot fight a giant monster, no beta we die like men, seriously dont think too much about it
Language: English
Status: Completed
Published: 2021-02-19
Updated: 2021-02-19
Packaged: 2021-03-15 09:33:43
Rating: Teen And Up Audiences
Warnings: Major Character Death
Chapters: 1
Words: 2,885
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/29557083
Author URL: https://archiveofourown.org/users/Shadowhisker/pseuds/Shadowhisker
Summary: A little fanfic for the Undertale AU "Inverted Fate" by Dorked, in which a giant robot piloted by Undyne fights a giant- well, Flowey once was a monster. He isn't anymore.(Massive Spoilers for Inverted Fate!)
Kudos: 5





	Inverted Fate: Determined Hearts

**Author's Note:**

> My first fic on here, and the first real writing I've done in a long time. Based off Inverted Fate by Dorked. Go read it; even if you didn't need to context to understand everything, it is just insanely good: https://invertedfate.com/
> 
> Also, this is half shitpost, so don't take it too seriously.

Frisk frantically dodged another volley of spears, the Hot Leg tight in their grip. Undyne limped after the human, her half metal face twisted in an expression that Frisk didn’t want to grace with a description. 

_We can’t keep up like this!_ Captain Cryptic (no, they were Chara, weren’t they?) shouted in Frisk’s mind. And on some level, Frisk knew their partner was right. They were out of items, they could **feel** their Determination wavering under Undyne’s onslaught, and their HP- “Gah!” -had dropped yet again, with the distinctive pain of a magic spear grazing against them. 

But what options were there? Undyne wouldn’t accept their Mercy, and there was nowhere to run. Frisk considered the weapon in their grasp. If there was no other choice, then maybe they would have to Fight. Undyne was close to killing them! She had hurt them so much! She was-

Frisk felt Cap do **something** that derailed their train of thought. And Frisk may have been stubborn, but Cap was right. They couldn’t Fight. Not after Asgore, and not after her. But what options were there?

You’ve got nowhere to run now,” Undyne growled. “We’ve hit rock bottom. Only one of us can make it out of here alive!”

Undyne’s words. Maybe there was something in what she had said, some sort of clue-

_“If I regained control of the timeline, I could go back. I could undo EVERYTHING that went wrong!”_

There. A flash of recollection. Going back, undoing everything. Not simply LOADing a SAVE, but RESETTING it all. All of their journeys, their friendships, it would be undone. But neither Frisk nor Undyne would have to die. 

Another spear strike. Frisk couldn’t take another hit like that. But it was okay, because it was their turn now. Digging deep in their SOUL, calling all the way back to the fall, and the flowerbed.

_Frisk, what are you DOING-_  
“Don’t you DARE-”

There was that **yank** of Undyne forcing Frisk back to her SAVE file, but they were doing something more than just a simple LOAD, but Undyne’s Determination was too strong, but Frisk still had strength of their own-

\--

And Frisk was falling through the air again. But they were surrounded by the metal of the CORE, not the stone of that first cavern. They activated their jetpack- just in time to dodge a swipe of the Determinator’s claws.

“You think you’re clever, don’t you?” Undyne’s growl, amplified by speakers, echoed throughout the CORE. “But you’re still here! And while I’m still breathing, you WON’T escape!”

_This is… good, actually,_ Cap mused. Frisk smirked. “You bet it is. I have all my items back, and I know what she can do now!”

“That’s the thing, punk! So do I!” Spears, overdriven by Determination, lashed not at Frisk, but their jetpack. The human fell down, desperately LOADING-

It was obvious that the fight would drag on. But Frisk had time, now.

\--

Flowey felt the timeline stutter **yet again.** What were they doing in there? The human (the human that wasn’t Chara, but somehow was) had half-RESET three times by now, and LOADED many more. They were stalemated with Undyne, it was obvious. But that meant his plans couldn’t move forward! It was all! So! Infuriating!

Time leapt back once more, and Flowey took the opportunity to vent his rage at the now-restored vending machine. That poor thing had endured so much abuse. Flowey breathed in and out heavily (always an odd feeling with only a mouth, and no lungs), watching as the target of his frustrations RESET into a pristine state.

“...Forget this. Six’ll just have to make do.” Despite everything, an evil grin crept across Flowey’s face. “No more playing games.” The Determination infused flower burrowed back into the dirt, and began speeding towards New Home.

The SOULs were probably in the same place as they were last time. He knew where they were, now. And even if they weren’t, that didn’t matter. Flowey had time, now.

\--

Undyne didn’t bother with spears or missiles or claws anymore. And Frisk didn’t bother with their blaster. Their Fight had become one of will, Determination clashing against Determination. Time turned backwards, continued forwards for a moment as human and monster caught their respective breaths, then stuttered once more. 

_How long are you going to keep going?_ “As long as it takes.”

Then, suddenly, something changed. An incomprehensible weight settled over Frisk’s SOUL. Undyne clearly felt it too, as the Determinator slumped, crashing into the wall. The gargantuan machine dug its claws into the metal, relying on raw strength instead of flight to keep from falling.

Everything was still for a moment. Eventually, Frisk spoke up. “...That wasn’t you, was it?” The Determinator’s massive head turned towards the hovering human. “If I could’ve done that, you’d be dead for good already, punk. Same goes for you, I’d guess.”

Captain Cryptic was oddly silent in the back of Frisk’s mind. “Cap? ...Chara? Do you know what just happened?”

A series of thick, thorn covered vines tore out of the walls, aiming for Frisk and Undyne both. Heavy breaths rattled through the CORE, as some **thing** descended from above. A thing made of flesh, plant tissue, and machinery. The television screen at the center of the monstrosity flickered briefly, before a familiar, petaled face appeared on screen.

_I can take a guess,_ Chara replied sardonically.

\--

Oh yes. The **power.** Flowey wasn’t complete, but it was exhilarating feeling the human SOULs wriggling inside him. But he couldn’t get distracted. Flowey had a job to do. Still, the feeling of such Determination pumping through him again…

The human was staring up at him in shock. He could almost see horror, the beginnings of betrayal, flashing through their little skull. “Flowey!? Why… You…” And here, the flower giggled. “Oh, I’m just moving up the timetable, **pal.** Cutting a few corners. And a boss monster, but there’s neither here or there.” The human was wrapped further in vines, and pulled closer to Flowey. They were still too shocked to even move, their eyes wide. Really, Flowey didn’t know why he ever thought they were Chara, if they were this weak. What was his best friend even doing with this human?

Flowey searched the human’s face, looking for a sign that they were listening. “Are you in there, Chara? You’re feeling left out, aren’t you?” The television screen showing his face flickered briefly. “Well, I have six SOULs. Just one more, and we-”

A surprise barrage of missiles slammed against the abomination, followed by several tons of metal and Determination. “Six SOULs?!” The Determinator shrugged off the vines sent its way, and dug its claws deeper into Flowey’s form. “' **Cutting boss monsters'?!** What did you do to the Queen!?” 

Oh. Right, the fish. Flowey rolled his eyes, and knocked her back with a combination of bombs, friendliness pellets, and the ever reliable buster beam. This was followed by a swift strike of thorny claws tearing away the Determinator’s chest plate, revealing-

Wow. That was one ugly fish. An ugly fish that was throwing spears like there was tomorrow; spears that didn’t do anything, of course. Flowey grinned cruelly, and crushed her under a claw, relishing in the squishiness of melting flesh, and the crunch of metal. Despite this, she didn’t die. Flowey’s smile turned into a grimace, and he pressed down harder, both physically and magically. Any second now…

Then, a scream, a human scream, and a **yank** on the timeline-

\--  
-And he was back in that waiting room again. He was empty again. Flowey screamed in fury, and burrowed under the floor. In a flash, he was before the barrier. Vines snaked under the earth, wrapped around the buried SOUL jars, and ripped them from the ground. The power of five SOULs was inside him now. No time to grab the sixth from dear old mom, but five would be powerful enough to cross the barrier.

In the end, it was back to Plan A.

\--

Undyne let out a shaky breath. That had been terrifying. The punk had saved her. Again. In any other case, it would’ve been infuriating, but that flower getting the SOULs changed everything. She couldn’t keep her promise if Toriel was dusted. The kingdom couldn’t bear a blow like that, even if they were free.

Then, the weight of several human SOULs slammed down on her again. Too late- this time, at least. Undyne reached out to a dial on the control panel near her, and twisted it so hard it almost snapped off. Determination flooded her veins. Hopefully it would be enough. If the punk could LOAD and RESET against that power, then Undyne could too, damn it! Warning sirens blared briefly before she shut them off, and Undyne gave the timeline a harsh **yank with all her might-**

-which countered by a sudden increase in **pressure** along the timeline. Crap. She just didn’t have enough. Not her own.

Wiping the fleshy half her forehead free of sweat, Undyne glared at the monitors in front of her. That kid- Frisk- was just hovering there, gripping their hand in their hands and muttering to themself. Probably talking to Chara, with a side of breakdown. Undyne certainly couldn’t imagine Papyrus turning on her like **that.**

Oh, crap, she was sympathizing with them now? Screw it, she needed their help anyways. It wouldn’t feel right ganking them while they were working through that betrayal. So, Undyne gritted her teeth and turned on the Determinator’s speakers.

\--

_Frisk, this isn’t your fault. I should have been honest with you from the start._

“Not my fault,” Frisk gritted out, tears streaming down their face. “Flowey’s taken the SOULs twice now. We can both feel it. That means he’s killed the Queen twice now! Everyone said she would never give the SOULs to anyone!”

Cap, their voice seething with frustration but obviously trying to be compassionate, responded. _If you would just calm down for a moment-_

“NO!” Frisk was all but screaming now. “I’m responsible for this! If I hadn’t taken so long with Undyne, if I had seen something from the start, if I had just listened to you…”

Whatever Chara might have said in response was preempted by a contralto voice. “Hey. Punk.” Frisk whipped around, heart pounding in their chest, and was greeted with the odd sight of the Determinator, still glowing red hot, but holding its hands up in a placating position.

Frisk eagerly shoved their horror and sense of betrayal aside for a familiar hatred. “Oh, NOW you want to talk, Undyne. Where was this conversationality twenty LOADs ago?” They folded their arms and glared at the mecha.

The Determinator folded its own arms, and returned the glare. “We don’t have time for this! We have to get out of here. Together, we have the Determination of... around four SOULs. We can beat up that flower enough to force a LOAD, and save Queen Toriel.”

“So, you want to team up,” Frisk growled, fists now clenched at the side. “After you killed me how many times?” They flew up close to the Determinator, and angrily pointed at it. “After what you did to Papyrus? Who’s a friend to both of us?!”

“I don’t like it either,” Undyne snapped back from inside her mecha. “But that doesn’t matter. None of that matters! Flowey has the SOULs. He’s already killed the Queen to get at them, who knows what he’ll do next!”

Frisk gasped at the reminder of who they would be teaming up to face. Those feelings of betrayal, of shock and horror, flooded back to the surface. Then, Cap spoke up once more.

_She’s right, Frisk. Besides, Undyne’s not offering to **not** kill you._ “Kind of a low bar, Cap,” Frisk replied in an empty tone. However, steel crept back into their voice as they looked up at the Determinator. “Fine. We have a truce. Let’s go.” The mecha only offered a nod in response. Then, both human and monster rocketed towards the top of the CORE, and towards New Home.

\--

In the Judgement Hall, there was a skeleton slumped against a pillar. Said skeleton was muttering knock knock jokes of increasingly poor caliber to himself in an attempt to keep his mind off things.

It wasn’t working.

The rumbling of something heavy landing on the balcony outside did, though. Sans opened his eyes in time to see Frisk and Undyne barging in side by side. Sans had never thought he would see the day.

“heya.” Monster and human screeched to a halt as he stepped out in front of them. It was then that Sans took in the extensiveness of Undyne’s cybernetics. He had known it was bad, but… “talk about surf and turf.”

“Can it, Sans,” Undyne all but growled. “Where’s Flowey.”

It was easy for Sans to see the kid flinch at the little weed’s name. If things had gone badly enough for Undyne and Frisk to stop fighting, then they were going **really** bad. “it’s already gone through the barrier. tori absorbed the last SOUL and followed. of course, that leaves us stuck on this side.”

The kid seized on his second to last statement. “Toriel’s still alive?” “yep,” Sans replied. “but she’s only got the one human SOUL against the five flowey has. ain’t gonna go well, if you ask me.”

Frisk brought their hand up to their chin, thinking for a moment. “Well… we aren’t stuck. Not really. It takes the power of a human soul and a monster soul to go through, right?” Undyne looked distinctly uncomfortable at this, while Sans’ gaze sharpened. It was the former who spoke first. “Punk... I already agreed to not kill you. And I don’t go back on my promises.”

“You don’t have to.” Frisk pointed back at the open door to the balcony, through which the parked Determinator could be seen. “We just have to join our Determination.” 

An odd look overtook Undyne, as a genuine smile grew on her face. “Punk. Are you telling me you want to pilot a giant robot together? To fight a giant monster?”

It was a smile Frisk mirrored. “That’s exactly what I’m telling you.”

Sans shrugged, and stepped away without a word. His work here was done. Now the fate of everything rested on the most unlikely allies the Underground had ever seen.

\--  
Flowey popped out of the ground, and gazed briefly at the setting sun. It was a sight that held bitter memories. The last time he had been on the surface…

That memory was shoved away, Flowey growling to himself. The sun didn’t matter. He just had to get two more SOULs, and then he would be **free**. **Free** of this stupid armless body, **free** to do whatever he wanted, **free** to be with his best friend again. 

Just a touch of the immense **power** he held was enough to sharpen his eyesight beyond even the most perceptive of hawks. Flowey looked around for any humans that might be isolated on the mountain. Instead, he saw something else.

He certainly hadn’t expected another warped creature that might have once been a boss monster to shamble down Mount Ebott. Flowey didn’t think the old hag had the guts; she’d had the SOULs for how long, and never left her throne? Hypocrite.

Flowey let his eyesight go back to normal, then used the SOULs to teleport behind his mother. The grotesque that was once Queen Toriel shuffled around, clutching her staff. “I do not know what you are,” she spat out from behind oversized fangs, “and I do not know what you intend to do with the SOULs. I demand that you return them to me. It is my duty to protect them”

**Power** ran wild through Flowey, as he assumed what he “affectionately” called his Omega form. “Oh, that’s rich,” the once-flower shot back. “Especially considering how easily you let me get these. You couldn’t protect them in life, and you couldn’t protect them in death.”

And here, Toriel was wrapped in a multitude of vines, locked into Blue mode, and surrounded by bullets of all kinds. “In fact, why don’t you let me borrow that last one?” Toriel glared at the abomination before her, flames erupting into existence all around mother and son. However, any SOUL seizing that might have happened was once more interrupted by a surprise barrage of missiles, followed by several tons of metal and Determination. 

The Determinator, it’s metal armor once more blue-green, the star on its chest glowing a brilliant red- red the color of certain amalgamated SOUL- stepped back, and slammed a fist into its palm. A clear challenge. Meanwhile, Toriel had slipped free of Flowey’s grasp, letting blue-hot flames gather along her staff. Flowey himself shifted backwards, readied his magic, lifted a pair of thorny claws, and gritted two sets of teeth.

There are things you can’t fight- acts of God, or beings close to it. You see a hurricane coming, you get out of the way. But when you have five hearts beating as one, three of those sitting in 250 tons of awesome? Suddenly, you can fight the hurricane. You can win. 

_*References to mecha movies from the early 21st century fill you with Determination. As does being in a mecha._


End file.
